1. Field of the Invention
The present invention relates to an image processing apparatus, an image processing method, and a computer-readable storage medium that can detect a feature in a plurality of consecutive images.
2. Description of the Related Art
In recent years, mixed reality (MR) technology has been known as a technology for seamlessly mixing a real world and a virtual world in real time. One kind of this MR technology is to provide a mixed reality image to a user with a video see-through head mounted display (HMD) or a handheld video display apparatus (handheld device (HHD)).
The video see-through HMD used for realizing the MR technology images an object that substantially matches an object observed from the position of eyes of the user by, for example, a video camera. The video see-through HMD provides a mixed reality space by displaying a captured image with computer graphics (CG) superimposed thereon to the user.
A technology of measuring the position and orientation of an HMD by detecting a feature point in a captured image, and arranging a virtual object at an appropriate position, to thereby superimpose CG on the captured image is known. Generally, the processing of detecting a feature point in a captured image produces a large processing load, and therefore it is required to effectively reduce the processing load even if only slightly. Reducing the processing load leads to a reduction in the power consumption as well, so that the operable time of the HMD can be increased if it is powered by a battery.
One method to reduce the processing load in the processing of detecting a feature point in a captured image is a method of comparing a feature point in a current frame with the result of detection of a feature point in an immediately preceding frame. The method discussed in Japanese Patent Application Laid-Open No. 2006-331108 performs a stereo measurement in two captured moving images positioned on an epipolar line. This Japanese patent application discusses that, in this method, the result of an immediately preceding frame is inherited to limit a target region in a current frame, if a feature point in one of the images captured by the two cameras is within the range of a predetermined value from the result of the immediately preceding frame.
In the method discussed in Japanese Patent Application Laid-Open No. 2006-331108 it is difficult to apply image processing to the left side and the right side independently, since this method is based on a stereo measurement, which requires detection of matching points in both the left and right captured images and confirmation whether they actually match each other by comparing them. Therefore, this method cannot provide sufficiently accurate processing when the HMD is in an inclined state, and cannot accomplish efficiency easily, so that this method is not suitable to an MR system.